Splitter design function and effects. Experience, Design knowledge?
08-21-2009, 03:43 PM
#106
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Hi Dave,
I do however have to challenge you regarding the venturi effect under the car, with a large splitter. I think that with a splitter, there is no incentive (force, differential pressure) to allow the build up of pressuer to go under the car, as the air moves to differential pressure and the lower pressure is over the car. the air under the car is a straight shot from oncoming air and is at near ambient pressure, as I have measured. Im sure there is still some spill over from the splitter, but its not measureable so far. could be my car is too high in theair, or needs side skirts to keep the pressure down , or lower under the car. surely, that is the concept and im far from Panneling the underbody yet, but its a long term goal. probably more important at the faster tracks, but we are so slow out in nor cal.
mk
I do however have to challenge you regarding the venturi effect under the car, with a large splitter. I think that with a splitter, there is no incentive (force, differential pressure) to allow the build up of pressuer to go under the car, as the air moves to differential pressure and the lower pressure is over the car. the air under the car is a straight shot from oncoming air and is at near ambient pressure, as I have measured. Im sure there is still some spill over from the splitter, but its not measureable so far. could be my car is too high in theair, or needs side skirts to keep the pressure down , or lower under the car. surely, that is the concept and im far from Panneling the underbody yet, but its a long term goal. probably more important at the faster tracks, but we are so slow out in nor cal.
mk
Also be careful when you say "air moves to differential pressure". That is true and is the "rest of the story" when you want to go beyond Bernoulli in describing lift as a total physical system...but in ground effect it is a somewhat different dynamic.
08-21-2009, 03:43 PM
#107
Rennlist Member
You are just bitter because you are self-impaling over & over again in true harakiri fashion, and because you apparently lack the brainpower to discern between "lose" and "loose".
Professional Racing and Driving Coach
Last edited by Veloce Raptor; 08-21-2009 at 04:34 PM.
08-21-2009, 03:47 PM
#109
This is the race we were you in. I suspect you were the black 911
http://www.youtube.com/watch?v=zCrMBe3j5ho
I thought we had 2 race that weekend.
If the second race is where I spun,and you passed me, good for you .
Thunderhill there was one race and I have alarcon floundering. want to see that video? I had to start in the back after being 15lbs too light to the unfair 3100lbs spec for my old bugger.
mk
http://www.youtube.com/watch?v=zCrMBe3j5ho
I thought we had 2 race that weekend.
If the second race is where I spun,and you passed me, good for you .
Thunderhill there was one race and I have alarcon floundering. want to see that video? I had to start in the back after being 15lbs too light to the unfair 3100lbs spec for my old bugger.
mk
Your clip shows only the beginning of the quali session on Sat. The race I was referring to is the Cup race we ran on Sunday. I have the in car video somewhere...
Yes I was in the darkblue, almost black 911.
08-21-2009, 03:56 PM
#111
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Thread Starter
Bryan,
yes, a splitter can add to the amount of vacuum under the car. It has to be designed that way, as the entire frontal area needs to be engeered to do so.
Generally, I have seen only ambient pressure under the car. If you want me to measure a specific spot I will. by the way, when my splitter collapsed in testing, it was curved down. just behind it became a low pressure zone. i woudl expect that would have changed further back.
To answer your question, yes, differenctial pressure top and bottom creates downforce on the structure, but also look at the change in pressure and flow over the car. this adds to it as claykos said.
as far as downforce on the structure, .32psi at 130mph is getting near the theoretical maximum. take that vs your splitter size and divide out the pressure. my 300square inch splitter is made out of 1/16" aluminum. it puts down 100lbs of downforce at 130mph. it can handle it with the cables ive mounted. it fails without them.
Bryan, get a clue. My front defusers in my 928, are used for cooling. not that all are, but some are. they grab under front air dam air flow and route it to the wheels and brakes.
yes, a splitter can add to the amount of vacuum under the car. It has to be designed that way, as the entire frontal area needs to be engeered to do so.
Generally, I have seen only ambient pressure under the car. If you want me to measure a specific spot I will. by the way, when my splitter collapsed in testing, it was curved down. just behind it became a low pressure zone. i woudl expect that would have changed further back.
To answer your question, yes, differenctial pressure top and bottom creates downforce on the structure, but also look at the change in pressure and flow over the car. this adds to it as claykos said.
as far as downforce on the structure, .32psi at 130mph is getting near the theoretical maximum. take that vs your splitter size and divide out the pressure. my 300square inch splitter is made out of 1/16" aluminum. it puts down 100lbs of downforce at 130mph. it can handle it with the cables ive mounted. it fails without them.
Bryan, get a clue. My front defusers in my 928, are used for cooling. not that all are, but some are. they grab under front air dam air flow and route it to the wheels and brakes.
They don't? You sure about that? Something doesn't have to be an actual air foil to create a low pressure zone. I didn't say a splitter was an airfoil, but that it acted similar (see the word: as) because they create a low pressure area underneath and a high pressure area on top. Do you disagree that there is a high pressure area on top of and a lower pressure area below a splitter?
In the case of some modern prototype cars, the front splitter really IS an air foil, with air flow above and below it and an adjustable angle of attack. There was much discussion about that during the coverage of LeMans this year.
Then why did your splitter need supports? Are you suggesting that the 150+ pounds of pressure that I've seen bend splitters (i.e. the splitters have bent at speed more than they bend when a small person stands on them) is only a small percentage of the overall downforce they create? I'm surprised I can't drive our car upside down...we must be be making 1000+ pounds of downforce from our front splitter alone.
Your "yes, right on" quote is in response to this:
Didn't you just disagree (in the first quote I provided) with the explanation that I linked to, stating that splitters do NOT work by creating a low pressure area underneath and converting the high pressure area at the front of the bumper into downward force?
What claykos says is in 100% disagreement with what you say (and near 100% agreement with the link I posted above that you previously disagreed with)...
...and yet you say he is "right on"? I think you're confused.
They have NOTHING to do with cooling. Cooling of the brake rotors is done by routing an air hose to the center of the rotor (often using a sealed duct around the rotor center) so that the cooling air can expand out through the vent vanes. Cooling of the caliper is done by ducting air directly at it. No one uses a diffuser on the front splitter to cool the brakes of their car. You show a seriously lack of understanding of (or even familiarity with) anything approaching modern race car aero and cooling with this statement alone.
In the case of some modern prototype cars, the front splitter really IS an air foil, with air flow above and below it and an adjustable angle of attack. There was much discussion about that during the coverage of LeMans this year.
Then why did your splitter need supports? Are you suggesting that the 150+ pounds of pressure that I've seen bend splitters (i.e. the splitters have bent at speed more than they bend when a small person stands on them) is only a small percentage of the overall downforce they create? I'm surprised I can't drive our car upside down...we must be be making 1000+ pounds of downforce from our front splitter alone.
Your "yes, right on" quote is in response to this:
Didn't you just disagree (in the first quote I provided) with the explanation that I linked to, stating that splitters do NOT work by creating a low pressure area underneath and converting the high pressure area at the front of the bumper into downward force?
What claykos says is in 100% disagreement with what you say (and near 100% agreement with the link I posted above that you previously disagreed with)...
...and yet you say he is "right on"? I think you're confused.
They have NOTHING to do with cooling. Cooling of the brake rotors is done by routing an air hose to the center of the rotor (often using a sealed duct around the rotor center) so that the cooling air can expand out through the vent vanes. Cooling of the caliper is done by ducting air directly at it. No one uses a diffuser on the front splitter to cool the brakes of their car. You show a seriously lack of understanding of (or even familiarity with) anything approaching modern race car aero and cooling with this statement alone.
08-21-2009, 03:58 PM
#112
Rennlist Member
Thread Starter
very high speed stepping motors , harmonic gear boxes and their associated drive and control electronics, and large axial flow, dual stage cooling fans.
08-21-2009, 03:59 PM
#113
Rennlist Member
Thread Starter
hey, i didnt say you didnt. I said loose. meaning , its waving in the wind. you might use some gel.
Lighten up francis.
OUT
mk
If brain power has to do with typos, yes, im hurting in that area. you too genius
Lighten up francis.
OUT
mk
If brain power has to do with typos, yes, im hurting in that area. you too genius
08-21-2009, 04:03 PM
#115
Rennlist Member
Thread Starter
That was a fun weekend. Heck we are racing buddies from many years ago.
That was a fun weekend. I hadnt been racing long, and you can see, that was my street car. I had a blast , even with all the extra weight POC had to saddle me up with. I get no credit?? I had my weight set bolted in the passenger compartment. I remember Dino doing the dive bomb move off the last straight in the race and I got a little too excited of the exit of the "hill". I did climb back to 4th. must have been right behind you.
good times. Like the video???
That was a fun weekend. I hadnt been racing long, and you can see, that was my street car. I had a blast , even with all the extra weight POC had to saddle me up with. I get no credit?? I had my weight set bolted in the passenger compartment. I remember Dino doing the dive bomb move off the last straight in the race and I got a little too excited of the exit of the "hill". I did climb back to 4th. must have been right behind you.
good times. Like the video???
08-21-2009, 04:08 PM
#116
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Thread Starter
If you read the posts from the beginning, you can see that its not.
I have already started thinking of improvments based on some of the inputs.
Everything I brought up to disucss was challenged and argued. too bad.
Im done here. I think we need to end it here.
I have already started thinking of improvments based on some of the inputs.
Everything I brought up to disucss was challenged and argued. too bad.
Im done here. I think we need to end it here.
08-21-2009, 04:12 PM
#117
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BTW, did you get my helpful tip in post #77? Just lookin' out for ya.
08-21-2009, 04:20 PM
#118
That was a fun weekend. Heck we are racing buddies from many years ago.
That was a fun weekend. I hadnt been racing long, and you can see, that was my street car. I had a blast , even with all the extra weight POC had to saddle me up with. I get no credit?? I had my weight set bolted in the passenger compartment. I remember Dino doing the dive bomb move off the last straight in the race and I got a little too excited of the exit of the "hill". I did climb back to 4th. must have been right behind you.
good times. Like the video???
That was a fun weekend. I hadnt been racing long, and you can see, that was my street car. I had a blast , even with all the extra weight POC had to saddle me up with. I get no credit?? I had my weight set bolted in the passenger compartment. I remember Dino doing the dive bomb move off the last straight in the race and I got a little too excited of the exit of the "hill". I did climb back to 4th. must have been right behind you.
good times. Like the video???
Dino was a demon on the brakes...he was still on the gas when we were already shutting down for the corner....
08-21-2009, 04:20 PM
#119
Rennlist Member
Thread Starter
Yes, I did. Thanks.
So... industrial-sized fans and their associated electric motors & controls. OK. Would have been simpler to say that the first time. "Digitally Controlled Motion Systems" sounds fancy but conveys no actual information.
BTW, did you get my helpful tip in post #77? Just lookin' out for ya.
BTW, did you get my helpful tip in post #77? Just lookin' out for ya.
08-21-2009, 04:21 PM
#120
Rennlist Member